Flat panel and projection devices are areas of rapidly growing display technology. Many of these technologies involve the filtering and modulating of light. Better resolution, brighter display, wider color gamut and greater contrast as well as lower production cost and lower energy usage are just a few of the goals of current research and development efforts.
Direct view flat panel displays include computer monitors and televisions as well as portable displays in cell phones, personal data systems, portable games, cameras, global positioning systems and many others. Current technologies such as plasma and liquid crystal displays (LCD) require significant energy to operate and are relatively costly to produce. Plasma is generally limited to displays over forty inches. The large number of thin film transistors (TFTs) that are fabricated in typical LCD's leads to quality control problems, much time spent on product inspection, and high rejection rates.
LCD-based displays require significantly brighter backlights with higher energy usage because of the need for polarization filters and color absorbance filters. Polarization filters absorb 60% of the source light and color filters absorb up to 75% of the source light. Along with the absorbance of other components in an LCD display, typically only about 5% of the source light is transmitted. As such, these devices have poor light and energy efficiency.
The picture quality of LCD displays is not optimal. First, the response time can be considered slow. Second, current LCD technology requires subpixels and provides lower resolution for a given number of electronic components, including thin film transistors and data drivers. Current LCD technology requires polarization and color filters that reduce brightness, provide a small color gamut and limit the number of primary colors that can be used at a time. And finally, LCD technology requires a fairly large number of electronic parts, including TFTs at each subpixel so that there is typically a large amount of black matrix associated with each pixel that does not transmit the source light.
There is a need for a direct view display that provides a high resolution with fewer subpixels per pixel with a concurrent reduction in electronic parts, including TFTs and data drivers. There is also a need for a display where the polarization and color absorbance filters are eliminated to provide greater brightness, a wider color gamut, more pure saturated color, and better contrast ratio. And there is a need for a display that uses light more efficiently, that eliminates polarization filters and color absorbance filters and minimizes dark matrix effects.
Current projection displays, such as digital micromirror devices (DMD), liquid crystal light valves (LCD) and liquid crystal on silicon (LCOS) have many of the same drawbacks as flat panel direct view displays. Current technology requires the use of polarization filters as used in LCD and LCOS. All three technologies can use three separate light valves to display three separate colors leading to increased manufacturing costs. If one light valve is used, then absorbance filter color wheels must be used. DMD requires expensive micromachining. Therefore, there is a need for a technology that offers superior picture quality to LCD, LCOS and DMD without the shortcomings inherent in these devices.
Based on the foregoing, it is clear that there is a need for light filters used in projection displays that can supply high contrast, wide color gamut with fewer than three light valves. There is also a need for technology that eliminates the need for polarization and color absorbance filters, with the resulting brighter display with a wider color gamut. It is also desirable to reduce the number of electronic parts to reduce the “screen door effect,” a negative effect seen in some LCD-based projection displays. There is also a need for a technology that provides full color control within one light valve without the use of absorbance color wheels. And there is also a need to provide more saturated colors, thus offering a clearer picture at high intensity with less washout. There is also a need for a projection display with high light efficiency that will transmit most of the source light. Additionally, it is believed that brighter displays may be achieved without the heat buildup that is characteristic of prior art projection display technology.
There is also a need for technology which improves the use of laser and LED arrays used as image formers for toner/fuser printers. For instance, there is a need for technology which allows for improved, multiple resolutions. Current devices use a complicated system of lasers and rotating mirrors and lenses, as is the case with current laser printers. As such, there is a need for a technology which is not limited by the size of the laser dot, as with laser technology, nor is it limited by the size of the LEDs in an LED array. And there is a need for technology which provides a less costly alternative to laser printers by eliminating the need for expensive lasers. Additionally, there is a need for greater speed so that whole lines can be projected across the imaging drum at a single time. There is also a need for finer detail than is available from current technologies because of the variation in light intensity that can be projected on the image drum.
It is also believed that improved light filters and associated arrays can be used in an image former for large format printers including lithography.
And finally, there is a need for a filter technology that is adaptable for use with digital cameras, video cameras, and other image formation devices, such as electronically tunable filters, spatial light modulators, spectroscopy devices, microscopy devices, holographics, data bus and wavelength division multiplexing (WDM) devices and large Fabry Perot interferometers.
There are a number of prior art devices that use various forms of polysiloxane which changes its physical properties upon application of an electric field. For example, a light modulator has been described having two deformable dielectric layers; where at least one dielectric layer is a relief-forming gel, such as a polyorganosiloxane gel, and the other layer is air. Reliefs are generated at the interface between the layers in response to signals applied to electrodes provided on either side of the dielectric layers.
Another prior art optical switching device manipulates an incident light wave passing through the device having an electrically controlled variable thickness plate. The device comprises a first transparent electrode; a second transparent electrode; and a layer of dielectric and transparent viscoelastic material located between the first and second electrodes that deforms in local thickness in response to an electric field. The transparent viscoelastic material includes silicone gel, oil, various polymer materials and other viscous substances that undergo viscous flow when placed in the presence of an electric field and relax towards their original form when the electric field ceases.
Another type of device is a control element that has been described having a liquid layer with electroosmotic movement to attain a geometrically uneven state in response to an electrical signal, having a high sensitivity to an applied voltage. The liquid layer contains at least one silicon compound, preferably a derivative of silane or siloxane including organopolysiloxane.
Still another device is a solid state light modulator that includes a charge storage device including a semiconductor substrate and associated with at least one display electrode; a deformable elastomer layer, a silica containing gel, such as a polydimethyl siloxane (PDMS); and a light reflective metal electrode layer. A potential applied between the display electrodes and the upper electrode causes the gel layer to deform in a rippled pattern.
A transparent film or coating composition blend of polysiloxane and liquid crystalline components has been used as an organic nonlinear optical unit in a light modulator device. The molecular orientation of the polysiloxane molecules can be external field-induced.
Some of the above devices require the polymer material to remain in a fluid or flowable condition. Thus, the completed assembly must be maintained in a flat, horizontal orientation. Even in devices where there is some type of adherence between the polymer material and the substrate, movement of the device may cause sagging of the polymer material, thus the light-altering properties of the polymer material cannot be sufficiently controlled. Some of the above devices require a thickness of more than 10 microns. Although these devices are believed to be effective for their stated purpose, their specific attributes and formulations are not conducive for use in displays. Therefore, there is a need in the art for a polysiloxane configuration which is adapted for use in light filters and light modulators that can be used in display type devices.